Lightguide fibers which are now producible are capable of competing favorably with other communication transmission media. This capability requires that economical splicing techniques be available for lightguide fiber systems. The linking of two fibers requires precise axial alignment and end separation. As one can imagine, the splicing of two lightguide fibers each having a diameter in the range of 50 microns is not an easy task. Splicing becomes even more of a problem for a plurality of lightguide fibers of an array such as, for example, a fiber ribbon which may comprise twelve individual fibers. The problem in splicing an array of fibers is to be able to position a first end of one array adjacent to a similar end of another array so that corresponding fibers are all in precise axial alignment.
A connector arrangement for splicing arrays of lightguide fibers is shown in U.S. Pat. No. 3,864,018, which issued on Feb. 4, 1975 in the name of C. M. Miller. Lightguide fibers are terminated in a duplicatable manner by a terminator in the form of substrates, which are called chips and which have spaced, parallel fiber-receiving grooves and ridges on top and bottom surfaces. Fibers of an array are held in aligned, opposing grooves of two chips, which are referred to as positive chips and which presently are made of a silicon material. The assembly of positive chips and fibers is potted to maintain the precision geometry of the array. A splice includes a butt joint of two such arrays which are aligned with respect to each other by so-called negative chips which span over the butted positive chips on each side of the assembly. The negative chips each have a plurality of grooves and ridges which are aligned with the ridges and the grooves of the positive chips to maintain the geometry. Clips are installed about the assembly to secure together the chips.
Methods and apparatus are available to facilitate the termination of lightguide fiber arrays with positive chips to prepare the fibers for splicing. For example, a vacuum chuck which may be used for such a purpose is described in an article by A. H. Cherin et al entitled "Vacuum-Assisted Silicon Chip Multifiber Chuck" as published in Vol. 16, of Applied Optics in June 1977. Also, in a process disclosed in U.S. Pat. No. 4,379,771 which issued on Apr. 12, 1983 in the name of D. Q. Snyder, a positive chip is positioned in a nest after which an end portion portion of a ribbon is moved longitudinally to cause the individual fibers to be separated by a comb-like device adjacent one end of the nest. Another positive chip is placed over the fibers so that the fibers are held in channels formed by the opposing grooves. Afterwards, the assembly of chips and fibers is held together with a vise which applies compressive forces to end portions of the assembly along a longitudinal centerline of the assembly. The vise is heated to cause a potting compound applied to the assembly to fill the interstices thereof to bond together the chips and fibers.
The assembly produced by the methods and apparatus of the aforementioned D. Q. Snyder patent includes lightguide fibers which extend from an end of the assembly and which must be severed. Also the chips must have planar end faces which are normal to the longitudinal axes of the fibers. In order to facilitate a connection of two lightguide fiber positive chip assemblies between the negative chips, those end faces must be profiled to have beveled top and bottom portions.
As should be expected, the geometry of the silicon chips of the assembly is very important from the standpoint of controlling transmission loss. Parameters of the chips must be maintained within very close tolerances. This matter is discussed in an article by D. Q. Snyder entitled "Lightguide Connector Component Characterization" which was published at page 209 in the preceedings of the International Wire and Cable Symposium that was held on Nov. 13 through 15, 1979.
What is needed are methods for end finishing an assembly of lightguide fibers and silicon chips. This must be accomplished so that one side of the end portion of the array of fibers measured transversely of the array is not out of plane more than six microns from the other side.